histo

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Author:
wdrusinowii
ID:
14304
Filename:
histo
Updated:
2010-09-16 19:44:15
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histology
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histology block 1
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  1. 
    • STRUCTURE:simple squamous
    • LOCATION: found in some kidney tubules, in alveoli of the lung, lining blood vessel,
    • and lining major body cavities
    • FUNCTION:Diffusion of gases
    • STRUCTURE: simple cuboidal
    • LOCATION: found covering the ovary, in some kidney tubules, forming thyroid follicles,
    • and lining many glandular ducts
    • FUNCTION:usually involved in secretion and resorption
    • STRUCTURE: simple columnar
    • LOCATION: Found in some glandular ducts, the gall bladder, the ovarian tube, the stomach and the intestine
    • FUNCTION:Movement of particles
    • OTHER:some specializations found include goblet cell inclusions (in the gut) and ciliated surfaces(such as insome tubes of the genito-urinary system)
    • STRUCTURE: stratified squamous
    • LOCATION: found on external surfaces (e.g. epidermis of the skin)
    • FUNCTION:can resist abrasion and entry of bacteria and water
    • STRUCTURE:stratified cuboidal or columnar
    • LOCATION:found lining many gland ducts
    • FUNCTION: Secretory
    • STRUCTURE: transitional epithelium
    • LOCATION: found in the ureter and urinary bladder
    • FUNCTION: designed to accommodate stretching of the organ
  2. 
    • STRUCTURE: Pseudostratified
    • LOCATION:seminal vesicle, upper respiratory tract, olfactory regions, epididymis and ductus deferens
    • FUNCTION: Absorption, movement of particles
    • OTHER: Can have cilia and goblet cells (for secretion and removal of contaminants), microvillia (odor detection), stereocilia (re-absorption)
  3. zonula occludens (tight junction) - seals between adjacent epithelial cells
  4. macula adherens (desmosome) - spot-shaped; binds to intermediate filament cytoskeleton of adjacent cells to bind cells together
  5. gap junction (nexus) - allow for direct communication between cytoplasmic compartments of adjacent cells
  6. 
    Simple tubular glands of the large intestine
    • Simple coiled tubular gland: sweat gland
    • Duct region and secertory region
  7. 
    • Myoepithelial cells
    • - basket-shaped, smooth muscle-like cells
    • - surround exocrine gland acini and contract in order to express acinar contents (e.g. mammary gland, sweat gland)
  8. 
    • Serous - proteinaceous secretions - watery consistency (e.g. parotid gland)
    • Mucous - glycoproteinaceous secretions: complex polysaccharides named mucus - viscous, gel-like consistency (e.g. sublingual gland)
    • Loose irregular CT
    • abundant ground substance, few fibres, and variable cell numbers

    contains many capillaries

    diffusion in ground substance facilitates waste and nutrient exchange with capillaries

    contains many immune cells to fight bacteria
    • DENSE IRREGULAR CT
    • •same as loose CT (Type I collagen & glycosaminoglycans), except that:

    •fibres are much larger & more tightly packed

    • •irregular fibres are specialized for strength such that DICT resists mechanical stresses in all directions (so keeps its shape)
    • •there is less ground substance
    • •there are fewer cells (mostly fibroblasts)
    • •such tissue forms:
    • –capsules & septa for many glands and organs

    –the periosteum (outer covering) of bone, perichondrium (outer covering) of cartilage, tendon & ligament sheaths, epimysium, epineurium, dura mater, submucosa of the GI and respiratory tracts, muscle fascia, and dermis of skin
    • DENSE REG CT
    • •tendons are made of tissue very like dense irregular CT

    –Type I collagen & glycosaminoglycans

    –minimal ground substance

    –mainly fibres & inactive fibrocytes, but fibres run in only one direction (along long axis of the tendon)

    –fibrocytes are arranged in rows between the fibres

    •ligaments are similar to tendons, but are more elastic

    –elastic ligaments are almost all elastin
  9. •highly specialized cells with a little loose CT

    • •fat cells are closely related to fibroblasts (same precursors)
    • •fat cells can make their own collagenous basement membrane

    •fat cells are metabolically very active

    •fat tissue develops from the 30th week of gestation to shortly after birth

    •mesenchymal stem cells replace adipocytes throughout life

    •two types of fat - white and brown
    • HYALINE
    • •cartilage is an avascular tissue

    •maintenance of cells depends upon diffusion of nutrients and oxygen from the vascularized perichondrium (outside layer)

    • •diffusion through the matrix (fibres and ground substance) provides nutrients and removal of waste metabolites
    • •growth continues slowly throughout life

    •pathology can occur when central cells die (e.g. due to lack of diffusion), and the matrix then will calcify

    • •if mechanical damage occurs, complete repair of cartilage does not occur
    • ELASTIC HAS ELASTIN FIBERS
    • BONE
    • §functions to provide skeletal support for the body and act as a storehouse of calcium

    §dynamic tissue, constantly changing in response to mechanical and other influences, and capable of repairing itself

    §ground substance is packed with calcium phosphate crystals and contains compact bundles of Type I collagen fibres, stem cells, osteoblasts, osteocytes, osteoclasts
    • Skeletal Muscle
    • •myoblast cells converge to make a muscle fibre = single, large (can be > 1 metre), multinucleated cell (a syncytium)
    • •connective tissue forms a support structure for the muscle fibre: facilitates the transfer of force to bones and provides a conduit for the vascular and neural supply to the muscle
    • –endomysium – surrounds individual muscle fibres

    –perimysium – surrounds muscle fascicles

    (i.e. groups of muscle fibres having the same motor innervation so that they contract together)

    –epimysium – surrounds a collection of fascicles; this is the fascia seen in the gross anatomy laboratory

    •within each cell, myofibrils form the functional unit

    –give the cells a striated appearance

    –myofilaments within myofibrils are the contractile elements of muscle
    • Cardiac Muscle
    • cardiac muscle fibres called cardiomyocytes:

    – striated

    –centrally located nucleus

    –large quantity of mitochondria (aerobic muscle)

    –t-tubule located at Z-line level

    –SER less developed and diads instead of triads

    –intercalated disk: complex intercellular cell junction comprising desmosome, fascia adherens and gap junction components

    –atrial myocytes have contractile function and endocrine function: production and secretion of natural diuretic hormones atrial natriuretic factor (ANF) and brain natriuretic factor (BNF)

    • Smooth Muscle
    • •originates from muscle mesenchyme
    • • no cross striations

    • has contractile myofilaments and intermediate filaments

    • intermediate filaments form a complex architecture with dense bodies being the equivalent of Z disc in other muscles

    • caveolae are permanent sarcolemmal invaginations (equivalent to the t-tubules of other muscles)

    • • sarcolemmal junctions are mainly gap junctions
    • •smooth muscle in some organs can regenerate by mitosis if injured
  10. 
    • NEURON
    • •consists of cell body (perikaryon or soma) and two types of branches: dendrites and an axon

    •the soma contains much rough endoplasmic reticulum (called Nissl substance or Nissl bodies) as well as normal complement of other organelles

    • dendrites tend to be relatively short and very branched and transmit information towards the soma

    •a single axon, arising from the axon hillock, transmits information away from the soma
    • Erythrocytes and Reticulocytes
    • -Erythrocytes are non-nucleated cells that use the molecule hemoglobin to carry oxygen from the lungs to peripheral cells and tissues

    -an increase in the numbers of reticulocytes indicates an increased need for oxygen, often the result of hemorrhage
    • Neutrophils
    • •involved in acute inflammation

    •engulf and destroy bacteria using pseudopodia (forming phagosomes)

    •lysosomes produce hydrolytic enzymes to help destroy phagosomes

    •specific granules of neutrophils also fuse to phagosomes to add hydrogen peroxide, myeloperoxidase, halide ions and other substances to help destroy bacteria

    •pus is a mixture of dead neutrophils and destroyed bacteria
    • Eosinophils
    • •involved in allergic reactions

    •increased numbers of these cells during such reactions result in eosinophilia

    •cells phagocytize antigen-antibody complexes formed in allergic responses

    •granule inclusions are toxic to parasitic worms

    •eosinophils are found particularly in the small intestine lamina propria , respiratory system (bronchi) and in the uterovaginal tract

    •eosinophils synthesize substances that inactivate histamine and leukotrienes (produced by basophils and mast cells) in order to reduce inflammatory reactions
  11. Basophils

    • •both basophils and mast cells contain granules containing heparin (anticoagulant) and histamine (vasodilator)
    • •both cell types participate in the inflammatory response to antigens

    •basophils are found in the peripheral blood circulation only; mast cells are found in connective tissue
    • Lymphocytes
    • •small lymphocytes in circulating blood are about the size of RBCs

    •large lymphocyte are activated by antigen; few in peripheral blood

    •lymphocytes enter connective tissues by diapedesis

    •these are the only leukocytes that can return to the circulation after migrating to the connective tissue

    •all lymphocytes originate in the bone marrow

    •T Lymphocytes mature in the thymus gland; their function is cell-mediated immunity: to destroy antigens (foreign cells, virus-infected cells, etc.)

    •B lymphocytes leave the bone marrow as mature cells; their function is to mature into plasma cells in the connective tissue and produce antibodies for the humoral immune response

    •T and B lymphocytes are found in the spleen, lymph nodes, and lymphatic nodules of the intestines
    • Monocytes
    • •monocytes are formed in the bone marrow
    • •they transit to the connective tissue via diapedesis

    •monocytes transform into macrophages after leaving the circulatory system

    •they form Kupffer cells of the liver, alveolar macrophages of the lung, osteoclasts in bone marrow, and antigen presenting cells (APCs). APCs concentrate antigen and present it to lymphocytes during an immune response
    • Platelets
    • •aggregation of platelets occurs in response to exposure to collagen at site of tear in blood vessel wall; a plug is formed by a clump of platelets

    -blood coagulation occurs when plasma proteins react to form fibrin from fibrinogen; fibrin forms a meshwork that traps blood cells to form a thrombus

    •clot retraction: the clot shrinks in response to actin and myosin of platelets

    •clot removal occurs after the vessel is repaired

    –plasminogen activator (from the endothelium) converts plasma plasminogen into plasmin; this is an enzyme that breaks down the clot

    –hydrolytic enzymes released from lambda granules aid in the dissolution of the clot

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